Adjusting speed limits to unexpected and varying situations such as weather conditions congestion or incidents can improve traffic flow. It will also enhance the safety and improve local air quality. By applying a flexible and wide range of speed limits, traffic management operators can influence the actual situation on the road. Thus road users can be allowed to "drive faster if possible and need to slow down if necessary". The Netherlands are already familiar with dynamic speed limits. In case of incidents motorists are required to drive at 70 or 50 kilometers per hour. Other reasons to reduce normal speed limits are extreme weather conditions and road works. But other applications are conceivable. Rijkswaterstaat is now researching the most promising of these developments in a number of field operational tests on different motorways.